Sophisticated electronic assemblies often employ dense arrays of electrical conductors to deliver signals from one area to another. Routing large groups of conductors in an efficient and organized manner often proves problematic for a variety of reasons. The overall assembly cost, form factor (size), conductor pitch, and complexity all typically must be taken into account to determine a suitable routing method.
For high performance semiconductor testers, sometimes referred to as automated test equipment or ATE, tester signals up to several gigahertz are funneled and delivered from relatively large circuit boards known as channel cards, to the leads of a very compact device under test or DUT. Often, several thousand signal paths provide the signal delivery scheme between the DUT and the tester electronics. In order to preserve fidelity for such high-frequency signals, the signal paths are constructed to provide as close to a matched fifty-ohm impedance as possible. Providing a closely matched impedance with a large number of signal paths is difficult.
One proposal for efficiently routing high performance signals in an automated test equipment interface is disclosed in U.S. Pat. No. 6,515,499, by Parrish, et al., entitled MODULAR SEMICONDUCTOR TESTER INTERFACE ASSEMBLY FOR HIGH PERFORMANCE COAXIAL CONNECTIONS, issued Feb. 4, 2003; assigned to Teradyne, Inc., Boston, Mass., herein incorporated by reference in its entirety. Generally, this proposal discloses a harness assembly for interfacing a plurality of semiconductor pin electronics circuits to a compliant interconnect array disposed on a device interface board or DIB. The harness assembly includes a plurality of cables having shield and center conductor distal tips that terminate in a housing. The distal tips of the cables are formed to define an interface engagement plane.
While this proposal above is beneficial for its intended purposes, the shield and center conductor contact structures are susceptible to a problem known as “pistoning”, due to the direct contact of the structures to the compliant array or interposer, and from bending of the cable. Pistoning involves the relative axial displacement of the center conductor with respect to the shield conductor. In some instances, if the pistoning problem is too great, the contact surfaces of the shield/signal conductors may be unable to touch the compliant interposer or the 50 ohm signal will be distorted. Complex contact configuration could address the problem, but at an undesirable cost when considering the thousands of connections involved.
One possible solution to the pistoning problem is disclosed in U.S. Pat. No. 6,686,732, by Frank Parrish, entitled LOW-COST TESTER INTERFACE MODULE, issued Feb. 3, 2004, assigned to Teradyne, Inc., Boston, Mass., herein incorporated by reference in its entirety. One disclosed form of the low-cost tester interface module provides a stiffener formed with a rectangular conductive body having an array of through-bores to receive coaxial cables. A signal transition assembly is bonded to the stiffener. The center conductors extend through drilled signal holes in the signal transition assembly, and are soldered therewith. After the signal conductors are installed and soldered, the DIB side of the signal transition assembly is milled to a desired flatness. The signal transition assembly is then plated to provide signal contacts. Although this tester interface provides high fidelity signals at low cost, because there can be thousands or more connections from a tester electronics card to a DIB, still lower cost, high fidelity, high frequency alternatives could further reduce the overall cost of the ATE.
Typically, a high performance machined connector is required to mate to a printed circuit board. A current state of the art high performance interface tends to cost around $50–$100 per line. Specific to the ATE market, these expensive connectors may be terminated to a printed circuit board or metal block, as discussed above, with pogo pins or other types of compliant interposers (such as FUJIPOLY ELASTOMERICS, by Fujipoly America, Carteret, N.J. or MPI by Tyco Electronics, Corp., wwww.tycoelectronics.com; C-LGA by InterCon Systems of Harrisburg, Pa.) being used to blind mate connect to the DIB. Such connectors also may be used to mate to any DIB variation, i.e., handler interface board or HIB, prober interface board or PIB, etc., or to other custom printed circuit boards or PCBs.
What is needed is a tester interface module capable of delivering high frequency, high fidelity signals at lower cost. Moreover, what is needed is a still lower cost method for manufacturing a tester interface module capable of high frequency and high fidelity.